We propose to extend and enrich a large longitudinal study of alcohol and other substance use disorders from adolescence through young adulthood that has been funded by NIAAA since 1991. Five waves of extensive diagnostic, medical, substance use and psychosocial functioning data have been collected from 565 adolescents from addictions treatment programs and a community comparison group of 220 youth: at baseline; at 1-year, 3-year, and 5-year follow-ups; and at age 25. The current project is designed to support continued analyses of this unique data set to study the long-term clinical course of adolescent-onset alcohol and drug problems and comorbid psychopathology; to extend this project to an age 30 assessment and study outcomes particularly relevant to this age; and, to support the collection of participants' DNA for current and future studies of genetic polymorphisms associated with alcohol and drug problem phenotypes. The age 30 assessment will include detailed self-report and interview data, DNA samples, a urine drug screen, a physical exam, and blood tests for HIV, HSV-2 and liver injury. Longitudinal data will be used to test two specific aims: 1) to characterize the validity of diagnostic criteria for AUDs/SUDs, and to determine pathways and predictors of the clinical course of these disorders, from adolescence through age 30; 2) to determine how adolescent and young adult substance use and problems affect and are affected by educational and occupational achievement, marriage, cohabitation and parenting. We also will describe and explore racial differences in young adult outcomes among African-Americans and Caucasians recruited from addictions treatment as teens. Very little work has addressed these important issues in clinical samples. The proposed research directly addresses NIAAA strategic priorities regarding the longitudinal study of adolescence and young adulthood; the importance of research on diagnostic criteria and comorbid psychopathology; the collection of DNA and the development of novel phenotypes in clinical research studies; and the study of racial differences in the effects of substance problems. The multidisciplinary research team has expertise in cross-fertilizing areas such as psychiatry, developmental psychopathology, genetics, statistics, criminal justice and public health. Our results will be directly translatable to clinical practice and public health policy. The extensive extant database (e.g., 3031 assessments in 785 subjects to date), the investigators' history of productivity and the emerging results regarding young adult outcomes of adolescent-onset addiction make this a highly feasible, critically important and cost-effective longitudinal project. Public Health Relevance: This project will study the Nosology and clinical course of alcohol and substance use disorders from adolescence through age 30. We will examine the effects of substance problem trajectories on young adult psychosocial functioning and potential racial disparities in these outcomes. The results will increase our understanding of how to prevent and treat adolescent and young adult substance disorders.